Verena Briner, Switzerland
Plastics are synthetic products that consist of organic polymers and additives such as bisphenol, ophthalates and flame retardants. Plastic is produced from coal, crude oil and natural gas, and it’s most useful properties are: it is easy to produce, hydrophobic, light, cheap and indestructible. Plastic has been widely used in toys, kitchenware, packaging, construction, electrical industry, machinery and other industries.
Due to its properties, the annual production of plastic has increased exponentially worldwide since the 1950s, and reached ca. 400 million tons per year worldwide in 2020. The 7 most used plastics are: polyethylene tetraphthalate (PET), high density polyethylene (PE), polyvinyl chloride (PVC), low density polyethylene (LDPE), polypropylene (PP), polystyrene (PS) and bisphenol (BP).
This durability is -on the other hand- the biggest disadvantage of plastic. Littering of single use- plastic products such as PET bottles, coffee cups, plates, bags, etc. results in enormous pollution. Worldwide only 9% of the plastic waste is recycled. Every year more than 2 million tons of plastic reach the sea and the world oceans. Up to 2020 more than 30 million tons of plastic accumulated in the oceans and up to 110 million tons in rivers. The major part of plastic decomposes into micro- (1-5 µm) (MP) and nano-plastics (1-1000nm) (NP).
The exposure to plastic is ubiquitous. It is estimated that humans ingest tens of thousands to millions of MP particles annually per person. Particles smaller than 20 µm cross biological membranes in the body. Plastics were once perceived as inert material doing no harm to human. However, its additives (>2400 are known) cause adverse effects. Additives such as phthalates (‘softener’) are forbidden in children toys in Europe but imported toys from foreign countries do not all have the same restrictions.
Plastic particles of <100 nm can cross the epithelial barrier of the skin and enter the lymphatic vessels and circulation or may cause local inflammation. The exposure of plastic to babies via the placenta is known and in animal experiments believed to enhance the risk of future cancer and impair fertility. Inhalation of micro-plastic causes accumulation in the lungs, and workers of flocking plants (nylon) may develop interstitial lung disease. Autopsies revealed plastic particles of <5.5 µm in the tissue. But at the present, scientific data in humans is still very limited.
A major plastic waste in lakes derives from tyre wear. MP and NP are distributed all over the planet but are not visible due to the small size. There are many other sources. The production of textiles contributes to the formation of microfibers. Currently, about 2/3 of the clothes are made of synthetic material such as polyester and polyamide, acrylic. During the washing procedure, microfibers are released into the water and finally into the lakes. Plastic microbeads are added to improve abrasive properties in toothpaste, shower gel, shaving cream, baby products, facial cleansers, etc. One facial scrub may release up to 90.000 plastic microbeads. MP are also added to pesticides and fertilizers.
Plastics have brought us a lot in terms of hygiene, safety and improvement of our quality of life. However, large quantities of MP and NP enter fish, mussel, shrimps, etc. in the sea. In agricultural sites plastic has been shown to contaminate vegetables, fruits, honey, beer. Eighty percent of tested tap water contained MP and water derived from plastic bottles contains more than 20 times higher concentrations of MP. Subsequently MP enters our body via oral intake of food, by inhalation, skin, wounds, hair follicles and sweat glands.
Cell cultures exposed to MP demonstrated signs of inflammation and cytotoxicity. Negative effects from plastic or its additives occur in several animal models on the immune and endocrine system (fertility and thyroid gland). The microbiome (bacteria) of the animal intestine changes by MP exposure and contributes to metabolic disorders and even colorectal cancer. In Western countries obesity seems not only the result of a disbalance between calories intake and output. Obesity promoting substances, called obesogens can activate nuclear hormone receptors and subsequently stimulate adipogenesis. PVC is a known obesogen.
It is well-known that Western diet disrupts the microbiome in human intestine and seems strongly associated with obesity. In addition, MP impairs the barrier function of the intestine and predisposes to inflammation. Plastic in the gut and other intestinal content enters the portal circulation and liver, impairs lipid metabolism and in the long term impairs liver function. In cell culture alteration of adipogenesis and energy metabolism could be confirmed. Therefore, some researchers link the increase of non-alcoholic fatty liver disease of human to the negative effect of microplastic.
Plastic will not totally be replaceable. A car will be several hundred kilos heavier when plastic is replaced by metal. A 500 ml glass bottle weights about 260 g, a PET bottle 13 g (in addition, there are negative effects on transport vehicles, roads, etc.). Plastic cover of cucumbers prolongs the freshness five times and thus reduces food waste.
To reduce plastic bag consumption, in Switzerland in 2016 the food stores had to charge 5 rappen (approximately 5 eurocents). There was a fall in consumption from 417.781.000 to 65.569.000 within 2 years. Yet replacing plastic bags by paper will increase the demand of trees considerably. Replacement of plastic is not always easy e.g. bicycle helmets, contact lenses, etc. A realistic goal should be to reduce plastic, re-use plastic (e.g. bags) and plastic waste should be recycled.
Summary:
- PET bottles and ‘hidden’ sources of plastic sources such as tyre wear, microfibers from synthetic textiles, microbeads in beauty products, pesticides and liquid plastic pollute the lakes and oceans, the arctic ice, the soil, the air.
- There is a knowledge gap in human research. Research is difficult in the field of MP and NP, which is encountered all over the world.
- Workers of flocking plants more frequently develop interstitial lung disease.
- Scientists have some evidence that PM and NP are important subfactors of general obesity in Western countries. The mechanism occurs via nuclear hormone receptors and may interfere with lipid metabolism.
- MP and NP and its additives penetrate the intestine and the lung epithelium in animal models to enter the blood circulation and thus all organs, even the brain. These models and cell cultures demonstrate toxic effects in lipid metabolism, fatty liver, thyroid function, fertility and fetal risk of later development of cancer.
- Plastic is durable for a very long time and will accumulate further. Therefore, we should stop using disposable plastic items (plates, cups, etc.) whenever possible, consume local brands (reduce transportation), re-use plastic (bags) whenever possible and recycle plastic.
